(1) Field of the Invention
The present invention relates to an autonomous hydrophone position locating and tracking system, and more particularly to a distributed array of buoy tethered autonomous hydrophone position locating apparatuses, where each such apparatus further includes a plurality of water velocity sensors deployed at selected depths along a cable that is connected at one end to a top side buoy that obtains buoy surface position data via a satellite based GPS link, and that is also connected at the other end to a bottom residing base unit that contains a hydrophone and also electronic signal processing components that receive the water velocity gradient data from the velocity sensors and the GPS position data from the surface buoy, and employs the data to determine the exact bottom location of that particular hydrophone which is then relayed to a satellite via the RF capable buoy antenna. Collectively the multi-hydrophone configuration provides an autonomous underwater hydrophone position locating and target tracking system that enables highly accurate position locating of the tracked objects. The system can be easily and quickly deployed to provide efficient underwater vehicle tracking. In addition, the system can be used to provide forward area anyplace-anytime test and evaluation range deployment capabilities.
(2) Description of the Prior Art
It is well known in the target tracking art to deploy a plurality of hydrophones over the ocean bottom in a dispersed pattern to effect a sensor string or array. However, the tracking accuracy of existing hydrophone sensor data output is greatly affected by the accuracy with which the relative position of the individual hydrophones is known in real time. Current methods for deploying hydrophone strings require that an expensive site survey be conducted to determine the initial bottom resting position of each individual hydrophone in the system. Over time, and especially for littoral water deployments, tether cables can be subjected to severe wave and tidal variations that may displace individual hydrophones over time which can in turn significantly impact the accuracy of overall system tracking solutions leading to a need to recalibrate. Recalibration of the deployed hydrophones presently requires that additional periodic costly site surveys be conducted. The need for further site surveys also prevents stealth deployment when tracking is desired in hostile waters.
What is needed is a way to overcome the inherent unreliable hydrophone position information associated with existing range systems by providing a quickly deployable acoustic hydrophone position locating system capable of continuous, accurate determination of each bottom deployed hydrophone's location in real time in order to permit the most accurate hydrophone string or array output data to the system.